Enhanced oil-based foam drilling fluid compositions and method for making and using same

ABSTRACT

New oil-based foam drilling fluids for oil and/or gas wells are disclose as well as methods of making and using same. The new oil-based drilling fluids including a base oil, a foaming agent and a polymer including at least one aromatic olefin monomer and at least one diene monomer, where the polymer improves foam properties rendering a foam stable at temperatures at or above 300° F. and even at temperatures at or above 350° F.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an oil-based foam drilling fluid foroil and/or gas wells and for methods of making and using same.

More particularly, the present invention relates to an oil-based foamdrilling fluid (OBFDF) for oil and/or gas wells, where the compositionincludes a base oil, a foaming agent, and a hydrocarbon soluble polymercomprising a polymer of a styrene monomer and a diene monomer, where thefoam is stable at a temperature of at least 350° F. The presentinvention also relates to methods of making and using same.

2. Description of the Related Art

Recently, an oil-based foam drilling fluid (OBFDF) was developed anddescribed in U.S. patent application Ser. No. 11/293,859 filed Dec. 2,2005. However, the use of this OBFDF fluid for underbalanced and nearbalance drilling applications is limited by undesirable foam stability(half life time) and undesirable temperature stability, when twoorganophilic phases (e.g., oil and nitrogen) are employed. When thecontinuous phase is crude oil, diesel, mineral oil, alpha olefins and/orester based oils and the foam gas is nitrogen, then the generation offoams that are stable at high temperatures is difficult and has not beenachieved to our knowledge.

Generally, to create a stable foam in such environments, foaming systemsincluding mainly fluoro surfactants and/or silicon based surfactants areused.

Alternatively and historically, the problem of generating a stable, hightemperature foam in fluids including two organophilic phases has beensolved either by changing the gas phase to carbon dioxide or slightlyviscosifying the liquid phase with ortho phosphate ester systems usingAl or Fe cross-linking agents or with other types of polymers. Thisalternative requires delicate balance in the amounts of the phosphateester and cross linking agent, which is difficult to manage by thoseskilled in the art.

Thus, there is a need in the art for an oil-based foam drilling fluidthat does not suffer from the deficiencies of prior art oil-basedfoaming systems and produces stable foams in fluids including twoorganophilic phases that are stable even in high temperatureenvironments.

SUMMARY OF THE INVENTION

The present invention provides an oil-based foam drilling fluid (OBFDF)comprising a base oil, a foaming agent, an oil or hydrocarbon solublepolymer and nitrogen, where the foam is stable at a temperature of atleast 350° F.

The present invention provides a method for preparing the oil-based foamdrilling fluids of this invention, where the method includespre-dissolving an oil or hydrocarbon soluble polymer in concentrationsbetween about 0.05 and about 10.0% w/w in a base oil. The method canalso include the step of adding a foaming agent to the fluid. The fluidsof this invention offer two fold advantages over prior art fluids: (1)increased base oil viscosity at low shear rates (0.06 l/s) above 40,000cP due to viscoelastic effects from the polymer additive, whichincreases the fluids ability to entrap an organophilic gas phase, and(2) reduced gravity drainage velocity through a plateau border betweenfoam cells.

The present invention provides a method for drilling an oil and/or gaswell including the steps of providing an oil-based foam drilling fluidof this invention. The method also includes the step of drilling an oiland/or gas well using the drilling fluid. The method also includesadding or injection an amount of a nitrogen-containing gas sufficient toproduce a stable foam so that a pressure of the fluid is less than orsubstantially equal to a fluid pressure of the formation into to whichdrilling is proceeding.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention can be better understood with reference to the followingdetailed description together with the appended illustrative drawings inwhich like elements are numbered the same.

FIG. 1 depicts a plot of a rheological profile of an embodiment of anoil-based foam drilling fluid of this invention at room temperaturefoamed with 300 psig of nitrogen at a quality of about 55%.

DEFINITIONS OF TERM USED IN THE INVENTION

The following definitions are provided in order to aid those skilled inthe art in understanding the detailed description of the presentinvention.

The term “amphoteric” refers to surfactants that have both positive andnegative charges. The net charge of the surfactant can be positive,negative, or neutral, depending on the pH of the solution.

The term “anionic” refers to those viscoelastic surfactants that possessa net negative charge.

The term “fracturing” refers to the process and methods of breaking downa geological formation, i.e. the rock formation around a well bore, bypumping fluid at very high pressures, in order to increase productionrates from a hydrocarbon reservoir. The fracturing methods of thisinvention use otherwise conventional techniques known in the art.

The abbreviation “RPM” refers to relative permeability modifiers.

The term “surfactant” refers to a soluble, or partially soluble compoundthat reduces the surface tension of liquids, or reduces inter-facialtension between two liquids, or a liquid and a solid by congregating andorienting itself at these interfaces.

The term “drilling fluids” refers to any fluid that is used during oiland/or gas well drilling operations.

The term “completion fluids” refers to any fluid that is used in oiland/or gas well completion operations.

The term “production fluids” refers to any fluid that is used in oiland/or gas well production operations.

An under-balanced and/or managed pressure drilling fluid means adrilling fluid having a circulating hydrostatic density (pressure) loweror equal to a formation density (pressure). For example, if a knownformation at 10,000 ft (True Vertical Depth—TVD) has a hydrostaticpressure of 5,000 psi or 9.6 lbm/gal, an under-balanced drilling fluidwould have a hydrostatic pressure less than or equal to 9.6 lbm/gal.Most under-balanced and/or managed pressure drilling fluids include atleast a density reduction additive. Other additive many include acorrosion inhibitor, a pH modifier and a shale inhibitor.

DETAILED DESCRIPTION OF THE INVENTION

The inventors have found that an oil-based foam drilling fluid can beformulated that has surprisingly high temperature stability attemperatures at or above about 300° F. in the presence of a gas such asa nitrogen-containing gas, without the need for added phosphoesters andcrosslinked viscosity enhancers. In certain embodiments, the foam havehigh temperature stability at temperatures at or above about 325° F. Inother embodiments, the foam have high temperature stability attemperatures at or above about 350° F. One difference between thecompositions of this invention and those of prior art teachings is thatcarbon dioxide is not used as gas phase in order to generate a stableoil-based foam. The inventors have found that the compositions of thisinvention are ideally well suited for forming foam with two organophilicphases: oil and a nitrogen-containing gas such as a cryogenic nitrogengas having an N₂ content greater than 99.99%, a membrane nitrogen gashaving an N₂ content of 93% or above, or any other nitrogen-containinggas having an N₂ content greater than 90%.

There is a great demand for oil-based foam drilling fluids in the oiland gas industry. Basically, these fluids have advantages overnon-oil-based foam drilling fluids including at least: improved drillbit lubricity, improved shale stability and improved penetration rate,making them attractive, especially in managed balanced drilling orunderbalanced drilling.

The inventors have found that by adding an oil soluble polymer includingat least one styrene monomer and at least one diene monomer in place ofthermally unstable phosphate esters, greatly improves foam properties.In addition to improving normal foam properties, the addition of thesepolymers increases high temperature stability, where the fluids now havestabilities at temperatures at or above about 300° F. In certainembodiments, the foam have high temperature stability at temperatures ator above about 325° F. In other embodiments, the foam have hightemperature stability at temperatures at or above about 350° F.

Drilling Fluids

Generally, a drilling fluid is used during the drilling of a well.Drilling fluids can be designed for so-called over-balanced drilling (ahydrostatic pressure of the drilling fluid is higher than the porepressure of the formation), under-balanced drilling (a hydrostaticpressure of the drilling fluid is lower than the pore pressure of theformation) or managed pressure drilling, where the hydrostatic pressureof the drilling fluid is managed depending on the nature of the materialthrough which drilling is occurring. Each type of drilling usesdifferent types of drilling fluids. The compositions of this inventionare designed to improve dispersion and stability of the resultingdrilling fluids so that cuttings remain suspended for longer periods oftime or at temperatures up to 350° F.

Compositional Ranges

The foamable hydrocarbon drilling fluids compositions of this inventionare defined on a volume percent (vol % or vol. %) basis based on 100 mLof a hydrocarbon base fluid. The foam composition is added to thehydrocarbon base fluid in an amount sufficient to achieve a desired foamheight (foam volume) and foam half life (time it takes to reduce by 50mL of the original foaming solution).

In certain embodiments, the foaming composition is added to thehydrocarbon base fluid in an amount sufficient to produce a foamablehydrocarbon drilling fluid capable of producing a foam having a foamheight between about 110 mL and about 200 mL or more and having a halflife between about 2 minutes and about 5 minutes or more.

Generally, the foaming composition is added to the hydrocarbon basedfluid in a weight percent (% w/w) ranging between about 0.05. % w/w andabout 5.0 vol. % w/w.

In different embodiments, the foaming agent is added to the hydrocarbonbase fluid in 1 percent (% w/w).

Generally, the polymer is added to the hydrocarbon based fluid in aweight percent (% w/w) ranging between about 0.05 and about 5.0% w/w.

Generally the amount of defoaming agent added to the foam drilling fluidsystems of this invention varies and might be about twice the amount offoaming agent added.

Foam Characteristics

Generally, the foamable hydrocarbon drilling fluid systems of thisinvention from an initial fluid amount of 100 mL, will produce a foamhaving a foam height of at least 140 mL and a half life of at least 2minutes. In particular, the produced foam will have a foam heightbetween about least 145 mL and about 150 ml depending in thecontamination in the foaming fluid and a half life above 3 minutes. Thestability or half life and foam height of the produced foam iscontrolled by the amount and type of the viscosifying agents in thecomposition, by the amount and type of the foaming agents in thecomposition, by the amount of gas and type of gas in the composition, bythe temperature of the composition and by the pressure of thecomposition. Generally, increasing the amount of the viscosifying agentsincreases the foam stability while increasing the concentration offoaming agents increases foam height. Of course, the foam height is alsodirectly proportional to the amount and type of gas dissolved orabsorbed in the fluid.

Suitable Reagents Hydrocarbon Base Fluids

Suitable hydrocarbon base fluids for use in this invention includes,without limitation, synthetic hydrocarbon fluids, petroleum basedhydrocarbon fluids, natural hydrocarbon (non-aqueous) fluids or othersimilar hydrocarbons or mixtures or combinations thereof. Thehydrocarbon fluids for use in the present invention have viscositiesranging from about 3×10⁻⁶ to about 600×10⁻⁶ m²/s (3 to about 600centistokes). Exemplary examples of such hydrocarbon fluids include,without limitation, poly-α-olefins, polybutenes, polyolesters,biodiesels, simple low molecular weight fatty esters of vegetable orvegetable oil fractions, simple esters of alcohols such as Exxate fromExxon Chemicals, vegetable oils, animal oils or esters, other essentialoil, diesel, diesel having a low or high sulfur content, kerosene,jet-fuel, white oils, mineral oils, mineral seal oils, hydrogenated oilsuch as PetroCanada HT-40N or IA-35 or similar oils produced by ShellOil Company, internal olefins (IO) having between about 12 and 20 carbonatoms, linear alpha olefins having between about 14 and 20 carbon atoms,poly-α-olefins having between about 12 and about 20 carbon atoms,isomerized α-olefins (IAO) having between about 12 and about 20 carbonatoms, VM&P Naptha, Linpar, Parafins having between 13 and about 16carbon atoms, HF-1000 (produced by Sasol, USA), and mixtures orcombinations thereof.

Suitable poly-α-olefins (PAOs) include, without limitation,polyethylenes, polypropylenes, polybutenes, polypentenes, polyhexenes,polyheptenes, higher PAOs, copolymers thereof, and mixtures thereof.Exemplary examples of PAOs include PAOs sold by Mobil Chemical Companyas SHF fluids and PAOs sold formerly by Ethyl Corporation under the nameETHYLFLO and currently by Albemarle Corporation under the trade nameDurasyn. Such fluids include those specified as ETHYLFLO 162, 164, 166,168, 170, 174, and 180. Well suited PAOs for use in this inventioninclude bends of about 56% of ETHYLFLO now Durasyn 174 and about 44% ofETHYLFLO now Durasyn 168. Other examples of PAO's include ChevronPhillips Grades PAO 2, PAO 4, PAO 6 and PAO 8 based on C₁₀ alphaolefins, and PAO 2.5, PAO 5, PAO 7 and PAO 9 based on C₁₂ alpha olefins.

Exemplary examples of polybutenes include, without limitation, thosesold by Amoco Chemical Company and Exxon Chemical Company under thetrade names INDOPOL and PARAPOL, respectively. Well suited polybutenesfor use in this invention include Amoco's INDOPOL “L” and “H” series,such as H-100, H-300, H-6000, and H-21000.

Exemplary examples of polyolesters include, without limitation,neopentyl glycols, trimethylolpropanes, pentaerythriols,dipentaerythritols, and diesters such as dioctylsebacate (DOS),diactylazelate (DOZ), and dioctyladipate.

Exemplary examples of polyolester include, without limitation, neopentylglycols, trimethylolpropanes, pentaerythriols, dipentaerythritols, anddiesters such as dioctylsebacate (DOS), diactylazelate (DOZ), anddioctyladipate.

Exemplary examples of petroleum based fluids include, withoutlimitation, white mineral oils, paraffinic oils, andmedium-viscosity-index (MVI) naphthenic oils having viscosities rangingfrom about 3×10⁻⁶ to about 600×10⁻⁶ m²/s (3 to about 600 centistokes) at40° C. Exemplary examples of white mineral oils include those sold byWitco Corporation, Arco Chemical Company, PSI, and Penreco. Exemplaryexamples of paraffinic oils include solvent neutral oils available fromExxon Chemical Company, high-viscosity-index (HVI) neutral oilsavailable from Shell Chemical Company, and solvent treated neutral oilsavailable from Arco Chemical Company. Exemplary examples of MVInaphthenic oils include solvent extracted coastal pale oils availablefrom Exxon Chemical Company, MVI extracted/acid treated oils availablefrom Shell Chemical Company, and naphthenic oils sold under the namesHydroCal and Calsol by Calumet and hydrogenated oils such as HT-40N andIA-35 from PetroCanada or Shell Oil Company or other similarhydrogenated oils.

Exemplary examples of vegetable oils include, without limitation, castoroils, corn oil, olive oil, sunflower oil, sesame oil, peanut oil, palmoil, palm kernel oil, coconut oil, butter fat, canola oil, rape seedoil, flax seed oil, cottonseed oil, linseed oil, other vegetable oils,modified vegetable oils such as crosslinked castor oils and the like,and mixtures thereof. Exemplary examples of animal oils include, withoutlimitation, tallow, mink oil, lard, other animal oils, and mixturesthereof. Other essential oils will work as well. Of course, mixtures ofall the above identified oils can be used as well.

Hydrocarbon Soluble Polymers

Suitable polymers for use in this invention include, without limitation,polymer comprising at least one aromatic olefin monomer and at least onediene monomer. The polymers can includes random polymers, blockpolymers, graft polymers, star polymers or other multi-armed polymers,which include one or more aromatic olefin monomers and/or one or morediene monomers or mixtures or combinations thereof. The term polymer asused herein refers to homo-polymers, co-polymers, polymers includingthree of more monomers (olefin monomers and/or diene monomers), polymerincluding oligomeric or polymeric grafts, which can comprise the same ordifferent monomer composition, arms extending form a polymeric center orstarring reagent such as tri and tetra valent linking agents ordivinylbenzene nodes or the like, and homo-polymers having differingtacticities or microstructures.

Exemplary examples of aromatic olefin monomers styrene,α-methyl-styrene, α-trifluoromethyl-styrene, fluorinated styrenes, wherethe fluorine atoms are disposed at ring positions or on ethylenylpositions, chlorinated styrenes, where the chlorine atoms are disposedat ring positions or on ethylenyl positions, alkylated styrenes, wherethe alkyl group are disposed at ring positions or on ethylenylpositions, vinyl-pyridine, alkylated vinyl-pyridines, where the alkylgroup are disposed at ring positions or on ethylenyl positions,fluorinated vinyl-pyridines, where the fluorine atoms are disposed atring positions or on ethylenyl positions, chlorinated vinyl-pyridines,where the chlorine atoms are disposed at ring positions or on ethylenylpositions, or mixtures or combinations thereof.

Exemplary examples of diene monomers include, without limitation,butadiene (B or BD), isoprene (2-methyl butadiene) (I), 2,3-dimethylbutadiene, 1,3-pentadiene, 1,3-hexadiene, or other similar 1,3-dienemonomers, or mixtures or combinations thereof.

Exemplary examples of polymers include, without limitation,styrene-isoprene copolymers (random or block), diblock polymers (SI),triblock polymers (SIS or ISI), multi-blocks (ISISIS, SISISI, etc.),styrene-butadiene copolymers (random or block), diblock polymers (SBR),triblock polymers (SBRS or BRSBR), multi-blocks (BRSBRSBRS, S BRSBRSBR,etc.), styrene-isoprene-butadiene copolymers (random or block), triblockpolymers (SBRI, SIBR, or ISBR), multi-blocks (SISBRS, SBRSIS, BRISIBRS,etc.), or mixtures or combinations thereof. Exemplary star polymersinclude polymers having a core and arm made of a polymer includingstyrene and I or BD. Other exemplary samples will include graft polymersof styrene and butadiene or isoprene.

Corrosion Inhibitors

Suitable corrosion inhibitor for use in this invention include, withoutlimitation: quaternary ammonium salts e.g., chloride, bromides, iodides,dimethylsulfates, diethylsulfates, nitrites, bicarbonates, carbonates,hydroxides, alkoxides, or the like, or mixtures or combinations thereof,salts of nitrogen bases; or mixtures or combinations thereof. Exemplaryquaternary ammonium salts include, without limitation, quaternaryammonium salts from an amine and a quatemarization agent, e.g.,alkylchlorides, alkylbromide, alkyl iodides, alkyl sulfates such asdimethyl sulfate, diethyl sulfate, etc., dihalogenated alkanes such asdichloroethane, dichloropropane, dichloroethyl ether, epichlorohydrinadducts of alcohols, ethoxylates, or the like; or mixtures orcombinations thereof and an amine agent, e.g., alkylpyridines,especially, highly alkylated alkylpyridines, alkyl quinolines, C6 to C24synthetic tertiary amines, amines derived from natural products such ascoconuts, or the like, dialkylsubstituted methyl amines, amines derivedfrom the reaction of fatty acids or oils and polyamines,amidoimidazolines of DETA and fatty acids, imidazolines ofethylenediamine, imidazolines of diaminocyclohexane, imidazolines ofaminoethylethylenediamine, pyrimidine of propane diamine and alkylatedpropene diamine, oxyalkylated mono and polyamines sufficient to convertall labile hydrogen atoms in the amines to oxygen containing groups, orthe like or mixtures or combinations thereof. Exemplary examples ofsalts of nitrogen bases, include, without limitation, salts of nitrogenbases derived from a salt, e.g.: C1 to C8 monocarboxylic acids such asformic acid, acetic acid, propanoic acid, butanoic acid, pentanoic acid,hexanoic acid, heptanoic acid, octanoic acid, 2-ethylhexanoic acid, orthe like; C2 to C12 dicarboxylic acids, C2 to C12 unsaturated carboxylicacids and anhydrides, or the like; polyacids such as diglycolic acid,aspartic acid, citric acid, or the like; hydroxy acids such as lacticacid, itaconic acid, or the like; aryl and hydroxy aryl acids; naturallyor synthetic amino acids; thioacids such as thioglycolic acid (TGA);free acid forms of phosphoric acid derivatives of glycol, ethoxylates,ethoxylated amine, or the like, and aminosulfonic acids; or mixtures orcombinations thereof and an amine, e.g.: high molecular weight fattyacid amines such as cocoamine, tallow amines, or the like; oxyalkylatedfatty acid amines; high molecular weight fatty acid polyamines (di, tri,tetra, or higher); oxyalkylated fatty acid polyamines; amino amides suchas reaction products of carboxylic acid with polyamines where theequivalents of carboxylic acid is less than the equivalents of reactiveamines and oxyalkylated derivatives thereof, fatty acid pyrimidines;monoimidazolines of EDA, DETA or higher ethylene amines, hexamethylenediamine (HMDA), tetramethylenediamine (TMDA), and higher analogsthereof, bisimidazolines, imidazolines of mono and polyorganic acids;oxazolines derived from monoethanol amine and fatty acids or oils, fattyacid ether amines, mono and bis amides of aminoethylpiperazine; GAA andTGA salts of the reaction products of crude tall oil or distilled talloil with diethylene triamine; GAA and TGA salts of reaction products ofdimer acids with mixtures of poly amines such as TMDA, HMDA and1,2-diaminocyclohexane; TGA salt of imidazoline derived from DETA withtall oil fatty acids or soy bean oil, canola oil, or the like; ormixtures or combinations thereof.

Other Additives

The drilling fluids of this invention can also include other additivesas well such as scale inhibitors, carbon dioxide control additives,paraffin control additives, oxygen control additives, or otheradditives.

Scale Control

Suitable additives for Scale Control and useful in the compositions ofthis invention include, without limitation: Chelating agents, e.g., Na,K or NH₄ salts of EDTA; Na, K or NH₄ salts of NTA; Na, K or NH₄ salts ofErythorbic acid; Na, K or NH₄ salts of thioglycolic acid (TGA); Na, K orNH₄ salts of Hydroxy acetic acid; Na, K or NH₄ salts of Citric acid; Na,K or NH₄ salts of Tartaric acid or other similar salts or mixtures orcombinations thereof. Suitable additives that work on threshold effects,sequestrants, include, without limitation: Phosphates, e.g., sodiumhexamethylphosphate, linear phosphate salts, salts of polyphosphoricacid, Phosphonates, e.g., nonionic such as HEDP (hydroxythylidenediphosphoric acid), PBTC (phosphoisobutane, tricarboxylic acid), Aminophosphonates of: MEA (monoethanolamine), NH₃, EDA (ethylene diamine),Bishydroxyethylene diamine, Bisaminoethylether, DETA(diethylenetriamine), HMDA (hexamethylene diamine), Hyper homologues andisomers of HMDA, Polyamines of EDA and DETA, Diglycolamine andhomologues, or similar polyamines or mixtures or combinations thereof,Phosphate esters, e.g., polyphosphoric acid esters or phosphoruspentoxide (P₂O₅) esters of: alkanol amines such as MEA, DEA, triethanolamine (TEA), Bishydroxyethylethylene diamine; ethoxylated alcohols,glycerin, glycols such as EG (ethylene glycol), propylene glycol,butylene glycol, hexylene glycol, trimethylol propane, pentaeryithrol,neopentyl glycol or the like; Tris & Tetrahydroxy amines; ethoxylatedalkyl phenols (limited use due to toxicity problems), Ethoxylated aminessuch as monoamines such as MDEA and higher amines from 2 to 24 carbonsatoms, diamines 2 to 24 carbons carbon atoms, or the like; Polymers,e.g., homopolymers of aspartic acid, soluble homopolymers of acrylicacid, copolymers of acrylic acid and methacrylic acid, terpolymers ofacylates, AMPS, etc., hydrolyzed polyacrylamides, poly malic anhydride(PMA); or the like; or mixtures or combinations thereof.

Carbon Dioxide Neutralization

Suitable additives for CO₂ neutralization and for use in thecompositions of this invention include, without limitation, MEA, DEA,isopropylamine, cyclohexylamine, morpholine, diamines,dimethylaminopropylamine (DMAPA), ethylene diamine, methoxy proplyamine(MOPA), dimethylethanol amine, methyldiethanolamine (MDEA) & oligomers,imidazolines of EDA and homologues and higher adducts, imidazolines ofaminoethylethanolamine (AEEA), aminoethylpiperazine, aminoethylethanolamine, di-isopropanol amine, DOW AMP-90™, Angus AMP-95, dialkylamines(of methyl, ethyl, isopropyl), mono alkylamines (methyl, ethyl,isopropyl), trialkyl amines (methyl, ethyl, isopropyl),bishydroxyethylethylene diamine (THEED), or the like or mixtures orcombinations thereof.

Paraffin Control

Suitable additives for Paraffin Removal, Dispersion, and/or paraffinCrystal Distribution include, without limitation: Cellosolves availablefrom DOW Chemicals Company; Cellosolve acetates; Ketones; Acetate andFormate salts and esters; surfactants composed of ethoxylated orpropoxylated alcohols, alkyl phenols, and/or amines; methylesters suchas coconate, laurate, soyate or other naturally occurring methylestersof fatty acids; sulfonated methylesters such as sulfonated coconate,sulfonated laurate, sulfonated soyate or other sulfonated naturallyoccurring methylesters of fatty acids; low molecular weight quaternaryammonium chlorides of coconut oils soy oils or C₁₀ to C₂₄ amines ormonohalogenated alkyl and aryl chlorides; quanternary ammonium saltscomposed of disubstituted (e.g., dicoco, etc.) and lower molecularweight halogenated alkyl and/or aryl chlorides; gemini quaternary saltsof dialkyl (methyl, ethyl, propyl, mixed, etc.) tertiary amines anddihalogenated ethanes, propanes, etc. or dihalogenated ethers such asdichloroethyl ether (DCEE), or the like; gemini quaternary salts ofalkyl amines or amidopropyl amines, such as cocoamidopropyldimethyl, bisquaternary ammonium salts of DCEE; or mixtures or combinations thereof.Suitable alcohols used in preparation of the surfactants include,without limitation, linear or branched alcohols, specially mixtures ofalcohols reacted with ethylene oxide, propylene oxide or higheralkyleneoxide, where the resulting surfactants have a range of HLBs.Suitable alkylphenols used in preparation of the surfactants include,without limitation, nonylphenol, decylphenol, dodecylphenol or otheralkylphenols where the alkyl group has between about 4 and about 30carbon atoms. Suitable amines used in preparation of the surfactantsinclude, without limitation, ethylene diamine (EDA), diethylenetriamine(DETA), or other polyamines. Exemplary examples include Quadrols,Tetrols, Pentrols available from BASF. Suitable alkanolamines include,without limitation, monoethanolamine (MEA), diethanolamine (DEA),reactions products of MEA and/or DEA with coconut oils and acids.

Oxygen Control

The introduction of water downhole often is accompanied by an increasein the oxygen content of downhole fluids due to oxygen dissolved in theintroduced water. Thus, the materials introduced downhole must work inoxygen environments or must work sufficiently well until the oxygencontent has been depleted by natural reactions. For system that cannottolerate oxygen, then oxygen must be removed or controlled in anymaterial introduced downhole. The problem is exacerbated during thewinter when the injected materials include winterizers such as water,alcohols, glycols, Cellosolves, formates, acetates, or the like andbecause oxygen solubility is higher to a range of about 14-15 ppm invery cold water. Oxygen can also increase corrosion and scaling. In CCT(capillary coiled tubing) applications using dilute solutions, theinjected solutions result in injecting an oxidizing environment (O₂)into a reducing environment (CO₂, H₂S, organic acids, etc.).

Options for controlling oxygen content includes: (1) de-aeration of thefluid prior to downhole injection, (2) addition of normal sulfides toproduct sulfur oxides, but such sulfur oxides can accelerate acid attackon metal surfaces, (3) addition of erythorbates, ascorbates,diethylhydroxyamine or other oxygen reactive compounds that are added tothe fluid prior to downhole injection; and (4) addition of corrosioninhibitors or metal passivation agents such as potassium (alkali) saltsof esters of glycols, polyhydric alcohol ethyloxylates or other similarcorrosion inhibitors. Exemplary examples oxygen and corrosion inhibitingagents include mixtures of tetramethylene diamines, hexamethylenediamines, 1,2-diaminecyclohexane, amine heads, or reaction products ofsuch amines with partial molar equivalents of aldehydes. Other oxygencontrol agents include salicylic and benzoic amides of polyamines, usedespecially in alkaline conditions, short chain acetylene diols orsimilar compounds, phosphate esters, borate glycerols, urea and thioureasalts of bisoxalidines or other compound that either absorb oxygen,react with oxygen or otherwise reduce or eliminate oxygen.

Salt Inhibitors

Suitable salt inhibitors for use in the fluids of this inventioninclude, without limitation, Na Minus—Nitrilotriacetamide available fromClearwater International, LLC of Houston, Tex.

Defoamers

Suitable defoaming agents for use in this invention include, withoutlimitation, any defoaming agent capable of reducing the foam height ofthe foamed drilling fluid systems of this invention. Exemplary examplesof defoaming agents are Dow Corning Antifoamers such as Dow Corning200(R).

Experiments of the Invention Foam Test

Foam test used a Lab Hamilton Beach Mixer. The test involves mixingdrilling fluids at high speed for 60 seconds and noting any change at 15second intervals. Foam concentrations tested are as set forth herein.After foaming on the mixer, the test drilling fluids were poured intoeither a 1,000 mL or 500 mL graduated cylinder to determine if the foammeasurement were linear. The foam height represented the mL occupied bythe foam after the foam was poured into the cylinder. The half liferepresents the time it takes to drain 50% of the original foamingsolution. If the foaming solution volume is 100 ml the half life time isthe one it takes to drain 50 ml of the liquid phase.

EXAMPLES

The following example illustrates the preparation of a variety ofoil-based foam drilling fluid in the absence and presence of a polymeradditive designed to illustrate the high temperature properties of thefoaming agent.

To 100 mL of “Off Road” Red Diesel #2 high sulfur content was added afoamer and optionally a polymer of this invention in the amountsindicated in the following table. The resulting solutions were foamedand a foam height and foam a half life were measured.

TABLE I Foam Properties of Hydrocarbon Foamer in Various Fluids FoamingSolution 100 mL 1% w/w Foamer* + 1% w/w Block 1% w/w Foamer* Copolymer**Foam Foam Volume Half Life Volume Half Life Fluid^(‡) (mL) (min:sec)(mL) (min:sec) None 186 2:50 180 4:00 5% of 3.5% Sea Water 162 2:00 1704:00 10% of 3.5% Sea Water 162 2:00 170 4:00 20% of 3.5% Sea Water 1602:00 170 4:00 5% Hatters Pond Condensate 170 2:15 170 4:00 10% HattersPond Condensate 180 2:20 160 4:00 ^(‡)Off Road Diesel #2 Base Fluid*Foamer DC-1250 **SV-150

Table II compares foam stability of the foam system when using Diesel asbase system and highly biodegradable HF-1000(Paraffin/Olefins/Oxygenated mixtures) as base system. Table III showsthe variation of the plastic viscosity and yield point in the foamingsolution at various concentrations of the block copolymer.

In FIG. 1, a plot of a rheological profile of an embodiment of anoil-based foam drilling fluid of this invention at room temperaturefoamed with 300 psig of nitrogen at a quality of about 55% is shown. Theaverage viscosity of the foam in the Newtonian range of a fluidincluding 1% w/w of the foamer in the absence of the polymer additivewas 9.72 cP, while the average viscosity of the foam in the Newtonianrange of a fluid including 1% w/w of the foamer in the presence of thepolymer additive was 16.85 cP. Comparative friction in the laminarregime showed a 73% increase in friction loss of the fluid with polymerwhile in turbulent regime an increase of 14% was observed.

TABLE II Foam Properties of Hydrocarbon Foamer in Various Fluids BaseOil 3.5% Sea Crude Aging Temperature Foam Half Life SystemConcentrations Water 3.0% KCL Condensate Oil ° F. (24 hr) Height (min.)Ave Recycle (10 times) Diesel 1% w/w DC-1250 + 170 4:00 Foam Height: 200mL 1% w/w SV-150 Half Time: 4:15 min Diesel 1% w/w DC-1250 + 10% 1704:00 1% w/w SV-150 Diesel 1% w/w DC-1250 + 20% 170 4:00 1% w/w SV-150Diesel 1% w/w DC-1250 + 30% 170 4:00 1% w/w SV-150 Diesel 1% w/wDC-1250 + 5% 160 4:00 1% w/w SV-150 Diesel 1% w/w DC-1250 + 10% 160 4:001% w/w SV-150 Diesel 1% w/w DC-1250 + 20% 160 4:00 1% w/w SV-150 Diesel1% w/w DC-1250 + 5% 160 4:00 1% w/w SV-150 Diesel 1% w/w DC-1250 + 10%170 4:00 1% w/w SV-150 Diesel 1% w/w DC-1250 + 20% 180 4:00 1% w/wSV-150 Diesel 1% w/w DC-1250 + 10% 160 4:00 1% w/w SV-150 Diesel 1% w/wDC-1250 + 20% 160 4:00 1% w/w SV-150 Diesel 1% w/w DC-1250 + 450 1604:00 1% w/w SV-150 HF1000 1% w/w DC-1250 + 170 0.166667 Foam Height: 200mL 1% w/w SV-150 Half Time: 4:15 min HF1000 1% w/w DC-1250 + 10% 1702:45 1% w/w SV-150 HF1000 1% w/w DC-1250 + 20% 160 2:40 1% w/w SV-150HF1000 1% w/w DC-1250 + 30% 160 2:30 1% w/w SV-150 HF1000 1% w/wDC-1250 + 5% 170 3:00 1% w/w SV-150 HF1000 1% w/w DC-1250 + 10% 160 2:451% w/w SV-150 HF1000 1% w/w DC-1250 + 20% 160 2:30 1% w/w SV-150 HF10001% w/w DC-1250 + 5% 170 3:00 1% w/w SV-150 HF1000 1% w/w DC-1250 + 10%160 2:40 1% w/w SV-150 HF1000 1% w/w DC-1250 + 20% 160 2:30 1% w/wSV-150 HF1000 1% w/w DC-1250 + 10% 180 3:00 1% w/w SV-150 HF1000 1% w/wDC-1250 + 20% 190 3:00 1% w/w SV-150 HF1000 1% w/w DC-1250 + 450 1603:40 1% w/w SV-150

TABLE III Rheological Properties of Red Diesel-Based Drilling Fluid^(#)Apparent Viscosity cP Yield Point Fluid^(‡) (300 RPM) lb/100 ft² 1% w/wFoamer* 5 1 1% w/w Foamer* + 1% w/w 13 2 Block Copolymer** 1% w/wFoamer* + 2% w/w 47 18  Block Copolymer** 1% w/w Foamer* + 5% w/w 253Too high to be Block Copolymer** measured ^(#)(Fan 35A Results UsingR1-B1) ^(‡)Off Road Diesel #2 Base Fluid *Foamer DC-1250 **SV-150

Example 2

Foam/Defoam cycle: Defoaming tests were made adding 2% w/w of defoamerDC 200 (R) fluid related to the foaming solution, which included 1% offoaming agent DC 1250 (foamer and defoamer are products of Dow Corning,USA) and 1% of polymer SV 150 (manufactured by Infineum, USA).Re-foaming tests were made adding 1% of the foaming agent. This cyclewas repeated at least 10 times obtaining foam half life time of at least4:00 minutes and foam height of 200 ml.

All references cited herein are incorporated by reference. Although theinvention has been disclosed with reference to its preferredembodiments, from reading this description those of skill in the art mayappreciate changes and modification that may be made which do not departfrom the scope and spirit of the invention as described above andclaimed hereafter.

1. A method for drilling a well comprising the steps of: adding aneffective amount of a foaming composition to a hydrocarbon base fluid toform a foamable hydrocarbon drilling fluid, where the foamingcomposition comprises a foaming agent and a stabilizing amount of apolymer, where the stabilizing amount of the polymer is sufficient toform a foam stable to a temperature of at least 350° F., pumping thefoamable hydrocarbon drilling fluid into a drill string while drilling,pumping an organophilic gas into the well at or near a distal end of thedrilling string or at or near a drill bit at a rate sufficient toproduce a foamed drilling fluid having a desired reduced fluid columnweight, where the foamed drilling fluid increases a fluid removal ratefrom the well and increase cuttings and other entrained materialsremoval from the well, and withdrawing the foam from the well.
 2. Themethod of claim 1, further comprising the step of: after the withdrawingstep, breaking the foam with a sufficient amount of a defoaming agent.3. The method of claim 2, further comprising the step of: repeating thetwo pumping steps, the withdrawal step and breaking steps at least 5times with or without adding an additional amount of the foamingcomposition or a component thereof.
 4. The method of claim 2, furthercomprising the step of: repeating the two pumping steps, the withdrawalstep and breaking steps at least 10 times with or without adding anadditional amount of the foaming composition or a component thereof. 5.The method of claim 1, wherein the foaming agent is selected from thegroup consisting of silicone foaming agents, fluorinated oligomeric orpolymeric foaming agents, and mixtures or combinations thereof.
 6. Themethod of claim 5, wherein the foaming agent is selected from the groupconsisting of DC-1250 available from Dow Corning, Zonyl FSG available,APFS-16 available from Applied Polymer, A4851 available from BakerPetrolite, Superfoam available from Oilfield Solutions, Paratene HFAavailable from Woodrising, DVF-880 available from Parasol ChemicalsINC., JBR200, JBR300, JBR400, and JBR500 available from JeneilBiosurfactant Company, Paratene HFA, Paratene HFB, Paratene MFA,Paratene MFB available from Woodrising Resources Ltd., and mixture orcombinations.
 7. The method of claim 1, wherein the hydrocarbon basefluid is selected from the group consisting of synthetic hydrocarbonfluids, petroleum based hydrocarbon fluids, natural hydrocarbon(non-aqueous) fluids or other similar hydrocarbons or mixtures orcombinations thereof.
 8. The method of claim 1, wherein the hydrocarbonbase fluid is selected from the group consisting of polyalphaolefins,polybutenes, polyolesters, vegetable oils, animal oils, other essentialoil, diesel having high or low sulfur content, crude oil, condensate,xylene, mineral sprits, low end kerosene cuts, VH&P Naptha, paraffin,Linpar parafins, kerosene, jet-fuel, internal olefins (IO) havingbetween about 12 and 20 carbon atoms, linear alpha olefins havingbetween about 14 and 20 carbon atoms, polyalpha olefins having betweenabout 12 and about 20 carbon atoms, isomerized alpha olefins (IAO)having between about 12 and about 20 carbon atoms, and mixtures orcombinations thereof.
 9. The method of claim 1, wherein the polymercomprises at least one aromatic olefin monomer and at least one dienemonomer.
 10. The method of claim 1, wherein the polymer comprises arandom polymer, a block polymer, a graft polymer, a star polymer or amulti-armed polymer or mixtures or combinations thereof, where thepolymers comprise one or more aromatic olefin monomers and/or one ormore diene monomers.
 11. The method of claim 9, wherein the aromaticolefin monomers comprise styrene, α-methyl-styrene,α-trifluoromethyl-styrene, fluorinated styrenes, where the fluorineatoms are disposed at ring positions or on ethylenyl positions,chlorinated styrenes, where the chlorine atoms are disposed at ringpositions or on ethylenyl positions, alkylated styrenes, where the alkylgroup are disposed at ring positions or on ethylenyl positions,vinyl-pyridine, alkylated vinyl-pyridines, where the alkyl group aredisposed at ring positions or on ethylenyl positions, fluorinatedvinyl-pyridines, where the fluorine atoms are disposed at ring positionsor on ethylenyl positions, chlorinated vinyl-pyridines, where thechlorine atoms are disposed at ring positions or on ethylenyl positions,or mixtures or combinations thereof.
 12. The method of claim 9, whereinthe diene monomers comprises butadiene, isoprene, 2,3-dimethylbutadiene, 1,3-pentadiene, 1,3-hexadiene, or other similar 1,3-dienemonomers, or mixtures or combinations thereof.
 13. The method of claim10, wherein the polymer comprise a random styrene-isoprene copolymer, adiblock styrene-isoprene polymer, a triblock styrene-isoprene polymer, amulti-block styrene-isoprene polymer, a random styrene-butadienecopolymer, a diblock styrene-butadiene polymer, a triblockstyrene-butadiene polymer, a multi-block styrene-butadiene polymer, arandom styrene-isoprene-butadiene copolymer, a triblockstyrene-isoprene-butadiene polymer, a multi-blockstyrene-isoprene-butadiene polymer, or mixtures or combinations thereof.14. The method of claim 10, wherein the star polymers comprise a coreand arms radiating out from the core, where the arms comprises polymersincluding styrene and isoprene and/or butadiene.
 15. A method fordrilling comprising the steps of: circulating a hydrocarbon drillingfluid system including a hydrocarbon fluid and an effective amount of afoaming composition into a borehole of an oil or gas well, where thefoaming composition comprises a foaming agent and a stabilizing amountof a polymer, where the stabilizing amount of the polymer is sufficientto form a foam stable to a temperature of at least 350° F., injecting anorganophilic gas into the fluid at a rate sufficient to form a foameddrilling fluid having a desired reduced fluid column weight, where thefoamed drilling fluid increases a fluid removal rate from the well andincrease cuttings and other entrained materials removal from the well,and withdrawing the foamed drilling fluid from the well.
 16. The methodof claim 15, further comprising the step of: breaking the foam with adefoaming sufficient amount of a defoaming agent.
 17. The method ofclaim 16, further comprising the step of: repeating the circulating,injection and breaking steps at least 5 times with or without adding anadditional amount of the foaming composition or a component thereof. 18.The method of claim 16, further comprising the step of: repeating thecirculating, injection and breaking steps at least 10 times with orwithout adding an additional amount of the foaming composition or acomponent thereof.
 19. The method of claim 15, wherein the foaming agentis selected from the group consisting of silicone foaming agents,fluorinated oligomeric or polymeric foaming agents, and mixtures orcombinations thereof.
 20. The method of claim 19, wherein the foamingagent is selected from the group consisting of DC-1250 available fromDow Corning, Zonyl FSG available, APFS-16 available from AppliedPolymer, A4851 available from Baker Petrolite, Superfoam available fromOilfield Solutions, Paratene HFA available from Woodrising, DVF-880available from Parasol Chemicals INC., JBR200, JBR300, JBR400, andJBR500 available from Jeneil Biosurfactant Company, Paratene HFA,Paratene HFB, Paratene MFA, Paratene MFB available from WoodrisingResources Ltd., and mixture or combinations.
 21. The method of claim 15,wherein the polymer comprises at least one aromatic olefin monomer andat least one diene monomer.
 22. The method of claim 15, wherein thepolymer comprises a random polymer, a block polymer, a graft polymer, astar polymer or a multi-armed polymer or mixtures or combinationsthereof, where the polymers comprise one or more aromatic olefinmonomers and/or one or more diene monomers.
 23. The method of claim 21,wherein the aromatic olefin monomers comprise styrene, α-methyl-styrene,α-trifluoromethyl-styrene, fluorinated styrenes, where the fluorineatoms are disposed at ring positions or on ethylenyl positions,chlorinated styrenes, where the chlorine atoms are disposed at ringpositions or on ethylenyl positions, alkylated styrenes, where the alkylgroup are disposed at ring positions or on ethylenyl positions,vinyl-pyridine, alkylated vinyl-pyridines, where the alkyl group aredisposed at ring positions or on ethylenyl positions, fluorinatedvinyl-pyridines, where the fluorine atoms are disposed at ring positionsor on ethylenyl positions, chlorinated vinyl-pyridines, where thechlorine atoms are disposed at ring positions or on ethylenyl positions,or mixtures or combinations thereof.
 24. The method of claim 21, whereinthe diene monomers comprises butadiene, isoprene, 2,3-dimethylbutadiene, 1,3-pentadiene, 1,3-hexadiene, or other similar 1,3-dienemonomers, or mixtures or combinations thereof.
 25. The method of claim22, wherein the polymer comprise a random styrene-isoprene copolymer, adiblock styrene-isoprene polymer, a triblock styrene-isoprene polymer, amulti-block styrene-isoprene polymer, a random styrene-butadienecopolymer, a diblock styrene-butadiene polymer, a triblockstyrene-butadiene polymer, a multi-block styrene-butadiene polymer, arandom styrene-isoprene-butadiene copolymer, a triblockstyrene-isoprene-butadiene polymer, a multi-blockstyrene-isoprene-butadiene polymer, or mixtures or combinations thereof.26. The method of claim 22, wherein the star polymers comprise a coreand arms radiating out from the core, where the arms comprises polymersincluding styrene and isoprene and/or butadiene.